1. Field
Embodiments of the present disclosure relate to an image forming apparatus, and more particularly, to an image forming apparatus in which a structure of a fusing device is improved.
2. Description of the Related Art
An image forming apparatus is a device for forming an image on a printing medium according to input signals, and examples thereof include printers, copiers, facsimiles, and all-in-one devices implemented by a combination thereof.
One type of an image forming apparatus, an electrophotographic image forming apparatus, includes a photosensitive unit having a photoreceptor therein, a charging unit which is disposed near the photosensitive unit and charges the photoreceptor to a predetermined potential level, a developing unit having a developing roller, and a light scanning unit. The light scanning unit applies light onto the photoreceptor charged to the predetermined potential level by the charging unit to form an electrostatic latent image on a surface of the photoreceptor, and the developing unit supplies developers onto the photoreceptor on which the electrostatic latent image is formed to form a visible image.
The visible image formed on the photoreceptor is directly transferred to the printing medium, or passes through an intermediate transfer material and then is transferred to the printing medium, and the visible image transferred on the printing medium is fused on the printing medium while passing through a fusing device.
Generally, a fusing device includes heating sources, fusing members formed with belts or rollers, and pressing members pressed against the fusing members and configured to form a fusing nip. When a printing medium to which a toner image is transferred is moved between the fusing members and pressing members, the toner image is fused on the printing medium by heat transmitted from the fusing members and pressure applied by the fusing nip.
Here, in the case of an image forming apparatus using a halogen lamp, a dual lamp is used to print paper sheets having various sizes. The dual lamp includes a center lamp and a side lamp which have the same size.
The center lamp and the side lamp have a difference in which densities of filaments are formed to be different in a longitudinal direction of each lamp to set different heat generation distribution for each lamp. Specifically, a central portion of the center lamp is formed to generate a large amount of heat, and both sides of the side lamp are formed to generate a large amount of heat.
In an image forming apparatus using the dual lamp including the center lamp and the side lamp, both of the center lamp and the side lamp are used when large-sized paper is printed, and only the center lamp is mainly used when relatively small-sized paper is printed.
However, since filaments are also disposed in both sides of the center lamp, even when a relatively small-sized paper is printed, both sides of the center lamp generate a small amount of heat. Accordingly, even when small-sized paper sheets are consecutively printed, fusing belts or rollers are overheated because a small amount of heat generated from both sides of the center lamp is accumulated therein, and thus a fusing device performs idling for cooling to address the accumulated heat. When the small-sized paper is printed as described above, there are problems in that overheating of both sides of the center lamp and idling of the fusing device to address the overheating degrade the performance of the image forming apparatus and decrease printing speed.